Diffuser for a turbocharger having an adjustable turbine geometry and turbocharger for an internal combustion engine

ABSTRACT

In a diffuser for a turbocharger having an adjustable turbine geometry wherein the diffuser comprises an axial slide and an adjusting device for moving the axial slide and wherein the adjusting device comprises an adjusting fork having an opening with a guide axis for the accommodation of a guide element and the adjusting device further comprises an adjusting lever with a lever end, the lever end is accommodated in a recess of the adjusting fork which is disposed at a side of the adjusting fork facing the axial slide in order to minimize tilting forces and provide for smooth sliding movement of the fork.

This is a Continuation-In-Part application of pending internationalpatent application PCT/EP2010/005201 filed Aug. 25, 2010 and claimingthe priority of German patent application 10 2009 050 975.5 filed Oct.28, 2009.

BACKGROUND OF THE INVENTION

The invention relates to a diffuser for a turbocharger having anadjustable turbine geometry operated by an actuating lever and to aturbocharger for an internal combustion engine including a turbinehaving such an adjustable turbine geometry.

From the application document US 2009 277171 A1, a diffuser for aturbocharger having an adjustable turbine geometry is known. Thediffuser comprises an axial slide and an adjusting device for thetranslational movement of the axial slide. The adjusting device in turncomprises an adjusting fork which encompasses the axial slide, a firstfork arm and a second fork arm each having a contact surface by means ofwhich a body contact with the axial slide can be established. A guidesection of the adjusting device has an opening for the accommodation ofa guide element. With the aid of the guide element, the axial slide canbe moved by an adjusting fork along a guide axis of the guide element,and therefore positioned securely. A lever end of an adjusting lever ofthe adjusting device engages the guide section. By means of theadjusting lever, movement of the adjusting fork can be initiated.

It is the principal object of the present invention to provide adiffuser for a turbocharger having an adjustable turbine geometry withan axial slide and a turbocharger for an internal combustion engine insuch a way that the axial slide can be moved without jamming in anyoperating range or operating directions while having a simple andcost-effective structure.

SUMMARY OF THE INVENTION

In a diffuser for a turbocharger having an adjustable turbine geometrywherein the diffuser comprises an axial slide and an adjusting devicefor moving the axial slide and wherein the adjusting device comprises anadjusting fork having an opening with a guide axis for the accommodationof a guide element and the adjusting device further comprises anadjusting lever with a lever end, the lever end is accommodated in arecess or groove of the adjusting fork which recess or groove isdisposed at a side of the adjusting fork facing the axial slide in orderto minimize tilting forces and provide for smooth sliding movement ofthe fork. The recess or groove has sidewalls forming guide surfaces incontact with the lever end.

The contact surface is designed to establish a contact between the axialslide and the adjusting fork. This means that there is a first point offorce application at the contact surface as the axial slide is beingmoved. A second point of force application for positioning the axialslide lies in the engagement recess, in which the lever end of theadjusting lever is accommodated for transmitting forces. As both of thepoints of force application which are required for the positioning ofthe axial slide are positioned with conformal directions, the initiatedmomentums can be compensated partially or even fully. As a result ofthis partial or full compensation, a tilting tendency of the adjustingfork and therefore a jamming in operation or during the positioning ofthe axial slide can be minimized.

In an advantageous variant of the diffuser, the engagement recess isprovided in a guide section of the adjusting fork, so that an adequatestrength of the adjusting fork is ensured while the axial slide is beingmoved.

In a further advantageous variant of the diffuser, the guide section isimmovably joined to the adjusting fork for further reducing the tiltingtendency.

In an advantageous variant of the diffuser, the lever end is movablypositioned in the engagement recess, so that, owing to this movablearrangement, a rotary movement of the adjusting lever and thus of thelever end can counteract a jamming of the lever end in the engagementrecess.

The engagement recess is positioned between the guide axis and alongitudinal axis of the axial slide, whereby the momentums developingin the positioning process are relatively small.

The invention further relates to a turbocharger for an internalcombustion engine, which turbocharger comprises a housing with anexhaust gas guide section and a wheel assembly with a turbine wheel,wherein a diffuser according to the invention is assigned to the exhaustgas guide section for controlling the admission of exhaust gas to theturbine wheel.

In a preferred variant of the turbocharger, a contact area having acertain length is formed between the adjusting fork and the guideelement, the guide element having a certain diameter. To reduce wear andto ensure a long service life for the turbocharger, a ratio between thelength and the diameter is advantageously greater than 2.

In a further variant of the turbocharger, the guide element is supportedin a contoured sleeve on the side remote from the turbine wheel and inthe exhaust gas guide section on the side facing the turbine wheel,thereby avoiding a distortion of the guide element if there are greattemperature fluctuations during engine operation.

In a further preferred variant, the guide element and its openings arecylindrical for cost-effective manufacture and simple assembly.

In a further advantageous variant, the adjusting fork and the axialslide have a first body contact and a second body contact, the firstbody contact and the second body contact being arranged to besymmetrical with respect to a guide axis of the guide element, whereby atilting movement of the axial slide can be avoided.

The invention will become more readily apparent from the followingdescription of advantageous embodiments thereof with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in a longitudinal sectional view an exhaust gas guidesection of a turbocharger according to the invention equipped with adiffuser;

FIG. 2 is a perspective view of a diffuser according to the invention;

FIG. 3 is a longitudinal sectional view of the exhaust gas guide sectionaccording to FIG. 1, with momentums acting on the diffuser while theaxial slide is being moved in a first direction;

FIG. 4 is a longitudinal sectional view of the exhaust gas guide sectionaccording to FIG. 1, with momentums acting on the diffuser while theaxial slide is being moved in a second direction;

FIG. 5 is a perspective view of a prior art diffuser;

FIG. 6 is a longitudinal sectional view of an exhaust gas guide sectionof a prior art turbocharger equipped with a diffuser according to FIG.5, with momentums acting on the diffuser while the axial slide is beingmoved in a first direction; and

FIG. 7 is a longitudinal sectional view of the exhaust gas guide sectionaccording to FIG. 6, with momentums acting on the diffuser while theaxial slide is being moved in a second direction;

In the figures, identical components or components of identical actionare identified by the same reference numbers.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

An internal combustion engine has a cylinder block with a cylinder headand a crankcase. The cylinder head is connected to a fresh air supplyline of the internal combustion engine and to an exhaust duct of theinternal combustion engine.

Cylinders are disposed in the cylinder block, each cylinder having anaxially movable piston supported therein. In addition, a crankshaft isrotatably mounted in the crankcase. Each piston is connected to thecrankshaft by means of a connecting rod, so that relevant piston forcescan be transmitted to the crankshaft and converted into a rotary motionof the crankshaft.

In the cylinders of the internal combustion engine, combustion chambersare formed for burning an air/fuel mixture. Each combustion chamber isbounded by an internal wall of a cylinder, by the piston movable in thecylinder and by a wall of the cylinder head, the wall of the cylinderhead and the respective piston being arranged opposite one another. Thevolumes of the combustion chambers can be varied by means of thepistons, so that a known combustion process can be carried out therein.

The cylinder head comprises an intake system with intake ports andintake valves and an exhaust system with exhaust ports and exhaustvalves, as well as an injection system for injecting fuel into therespective combustion chamber, the fuel being delivered by means of afuel pump from a fuel tank. Each intake port preferably has at least oneintake valve by means of which the intake port can be opened or closed,the intake valve being located at an end of the intake port which facesthe combustion chamber. Via the intake port, combustion air or anair/fuel mixture can be fed to the combustion chamber while the intakevalve is open. An end of the intake port which is remote from thecombustion chamber is connected to an inlet manifold which is located inthe fresh air line and has the purpose of steadying flow.

Each exhaust port preferably has at least one exhaust valve by means ofwhich the exhaust port can be opened or closed, the exhaust valve beinglocated at an end of the exhaust port which next to the combustionchamber. During the combustion of the air/fuel mixture formed in thecombustion chamber, the internal combustion engine produces exhaust gaswhile in operation; this can flow into the exhaust duct through theexhaust port.

The fresh air line comprises a charge air line, the inlet manifold beinglocated at an end of the charge air line next to the internal combustionengine. Upstream of the inlet manifold, an intercooler is provided inthe charge air line for cooling compressed combustion air. An air filterfor cleaning the combustion air is provided at the inlet end of thecharge air line, remote from the internal combustion engine.

The exhaust tract comprises the exhaust manifold and an exhaust gasline, the exhaust manifold comprises exhaust gas passages and a headerwhere the exhaust gas passages merge. The exhaust manifold is positioneddownstream of the cylinder head exhaust system, one exhaust gas passagebeing assigned to each exhaust port. At an opening of the header, theexhaust gas line is connected to the exhaust manifold, the opening beingpositioned downstream of the exhaust gas passages. At an end of theexhaust gas passage which is remote from the internal combustion engine,an exhaust treatment system is provided for treating the exhaust gas,the exhaust treatment system including a particulate filter and/or acatalytic converter.

In addition, the internal combustion engine comprises an exhaust gasrecirculation system, with a connecting line acting as an exhaust gasrecirculation line being provided between the exhaust manifold and theintake manifold. In the exhaust gas recirculation line, an exhaust gasrecirculation cooler is provided to cool recirculated exhaust gas. Therecirculated amount of exhaust gas is adjusted by means of an exhaustgas recirculation valve.

For the closed- and open-loop control of many functions, a closed- andopen-loop control system is assigned to the internal combustion engine.Via the closed- and open-loop control system, the fuel supply and theexhaust gas recirculation valve can be controlled in particular.

The internal combustion engine is provided with a turbocharger 1 with ahousing 2 comprising an air duct section not shown in detail, throughwhich air can flow, an exhaust gas duct section 3, through which exhaustgas can flow, and a bearing section, wherein the air duct section islocated in a fresh air line not shown in detail and the exhaust gas ductsection 3 is located in an exhaust not shown in detail.

The turbocharger 1 comprises a wheel assembly not shown in detail, whichin turn comprises a compressor impeller for drawing in and compressingcombustion air, a turbine wheel for expanding exhaust gas and a shaftwhich joins the compressor impeller to the turbine wheel for rotationabout a common axis of rotation. The shaft is rotatably mounted in abearing section of the turbocharger 1, which bearing section is notshown in detail and is positioned between the air duct section and theexhaust gas duct section 3.

In the air duct section, which is not shown in detail in the drawing,the compressor impeller is rotatably positioned in a first wheelchamber. Upstream of the first wheel chamber, an inflow passage isprovided in the air duct section, the inflow passage and the compressorimpeller being preferably coaxial. The inflow passage is used forconditioning the combustion air drawn in by the compressor impeller.

Downstream of the first wheel chamber, an outflow passage in the form ofa diffuser is formed in the air duct section; this is designed forconditioning the combustion air drawn in and compressed by thecompressor impeller. At the end remote from the first wheel chamber, theoutflow passage is connected to a first spiral passage which forms partof the air duct section and which is used for providing a rotationallysymmetric flow. The first spiral passage is further designed as aconnecting passage between the outflow passage and an outlet passageformed in the air duct section.

In an alternative embodiment of the air duct section, the air ductsection comprises a device for controlling the air flow to thecompressor impeller. As a result of this air flow control, an expansionof the drawn-in combustion air is possible, so that the compressorimpeller can operate in a cold air turbine mode.

For an exhaust gas flow into the exhaust gas duct section 3, an inletpassage 4 is formed in the exhaust gas duct section 3. The inlet passage4 is used for conditioning the exhaust gas, which makes the turbinewheel rotate during operation of the internal combustion engine. Theinlet passage 4 is preferably perpendicular to the axis 14 of rotationof the shaft.

Downstream of the inlet passage 4, a second spiral passage 5 is providedin the exhaust gas duct section 3; this is used for providing arotationally symmetric flow. Downstream of the second spiral passage 5,a feed passage 6 is provided in the exhaust gas duct section 3, whichfeed passage 6 is generally designed for conditioning the flow of theexhaust gas. The second spiral passage 5 is further designed as aconnecting passage between the inlet passage 4 and the feed passage 6.Downstream of the feed passage 6, a second wheel chamber 7 is providedin the exhaust gas duct section 3, the turbine wheel not shown in detailin the drawing being positioned in the second wheel chamber 7. At theend adjacent to the second wheel chamber 7, the feed passage has anorifice cross-section 8. Downstream of the second wheel chamber 7, anoutlet passage 9 is provided in the exhaust gas duct section 3.

During the operation of the internal combustion engine, the turbinewheel is made to rotate as a result of the admission of the exhaust gasof the internal combustion engine, and in this process, the shaftrotates the compressor impeller as well, so that it draws in andcompresses combustion air.

In order to achieve an efficiency of the turbocharger as high aspossible both at low loads and speeds of the internal combustion engineand at high loads and speeds of the internal combustion engine, theexhaust gas can be conditioned by means of an adjustable diffuser 10installed into the exhaust gas duct section 3.

As shown in FIG. 1, the diffuser 10 comprises a guide vane ring 11through which exhaust gas flows, an annular axial slide 12 and acontoured sleeve 13 for conditioning the flow of exhaust gas in theoutlet passage 9. The guide vane ring 11, the axial slide 12 and thecontoured sleeve 13 are coaxial with the shaft, i.e. the axis ofrotation of the shaft of the wheel assembly corresponds to alongitudinal axis 14 of the axial slide 12. The contoured sleeve 13 isimmovably positioned in the exhaust gas duct section 3. The guide vanering 11 is fixed in the exhaust gas duct section 3.

The guide vane ring 11 partially encloses the turbine wheel in the feedpassage 6, the guide vane ring 11 projecting into the orificecross-section 8. The axial slide 12 has a first recess 15 which facesthe guide vane ring 11 and in which the guide vane ring 11 can beaccommodated. By means of the axial slide 12, the size of the orificecross-section 8 can be adjusted. The orifice cross-section 8 ispreferably small at low loads and/or speeds of the internal combustionengine and large at high loads and/or speeds of the internal combustionengine.

An adjusting device 16 is assigned to the axial slide 12. The adjustingdevice 16 comprises an adjusting fork 17 with a guide section 18, aguide element 19 and an adjusting lever 20. A force acting on theadjusting lever 20 to initiate adjustment can be provided electricallyand/or mechanically and/or pneumatically and/or hydraulically.

The adjusting fork 17 is U-shaped (see FIG. 2). A first curved fork arm21 and a second curved fork arm 22 are joined to the guide section 18 atthe ends adjacent to the guide section 18 for movement therewith. Thefirst fork arm 21, and the second fork arm 22 are symmetrically arrangedopposite each other and convex with respect to the guide section 18between the first fork arm 21 and the second fork arm 22.

The guide section 18 has an opening 23 extending through the whole ofthe guide section 18, which opening 23 is parallel to the longitudinalaxis 14. At right angles to the guide axis 24, the guide section 18 hasa groove-shaped engagement recess 25 at the surface which faces theaxial slide 12.

For the secure guidance of the adjusting fork 17, the guide element 19has a cross-section complementing the opening 23. A symmetricalcross-section is preferred.

The guide element 19 is preferably cylindrical in design and has aneffective diameter D. In order to ensure a secure guidance, the guideelement 19 is firmly joined to the contoured sleeve 13 at its end remotefrom the spiral passage 5. At its end, facing the spiral passage 5, theguide element 19 is axially freely movable supported in the exhaust gasduct section 3, as a result of which a distortion of the guide elementby temperature fluctuations can be avoided.

The adjusting fork 17 is bearing-mounted on the guide element 19, theguide element 19 extending through the preferably cylindrical opening23. Owing to the bearing-mounted arrangement, a contact area 26 havingthe length L is formed between the guide element 19 and the adjustingfork 17. To avoid a tilting movement of the adjusting fork 17, theeffective diameter D of the guide element 19 is preferably chosen suchthat the length L is greater than the effective diameter D; inparticular, an L/D ratio greater than 2 should be chosen between thelength L and the effective diameter D.

The adjusting lever 20 has a first lever arm 27 with a pin-shaped leverend 28 and a second lever arm 29. The first lever arm 27 and the secondlever arm 29 are firmly joined together opposite each other by aconnecting bar 30, the lever end 28 being arranged adjacent to theengagement recess 25. The adjusting lever 20 is rotatably mounted in theexhaust gas duct section 3 by means of the connecting bar 30, which isaccommodated in a bushing 31, in order to absorb adjusting forces. Owingto the pin-shaped design of the lever end 28, any movement involves lessfriction as a result of a localized or linear contact between thepin-shaped lever end 28 and the engagement recess 25.

The lever end 28 is designed to engage the engagement recess 25, apositive guidance of the lever end 28 being provided in the engagementrecess 25. The lever end 28 is preferably positioned movably andincludes a sliding roller structure, so that wear and jamming in theengagement recess 25 in operation can be avoided.

As FIG. 2 shows, the adjusting fork 17 encompasses the axial slide 12,wherein a first end section 32 of the first fork arm 21, which is remotefrom the guide section 18, and a second end section 33 of the secondfork arm 22, which is remote from the guide section 18, engage agroove-shaped second recess 34 of the axial slide 12, which recessextends around the axial slide 12. Between the second recess 34 and afirst contact surface 35 of the first end section 32, which isaccommodated in the second recess 34, a first body contact is formed. Inorder to counteract any tilting motion of the axial slide 12, a secondbody contact is formed between the second recess 34 and a second contactsurface 36 of the second end section 33, which is accommodated in thesecond recess 34 and is concealed in the perspective view, wherein thefirst body contact and the second contact should be symmetrical withrespect to the guide axis 24.

For positioning the axial slide 12, an adjusting force acting on thesecond lever arm 29 is generated by means of an actuator. As theadjusting lever 20 is mounted rotatably, the first lever arm 27 performsa rotational movement as a result of its fixed connection to the secondlever arm 29. This rotational movement is converted into a translationalmovement of the adjusting fork 17 owing to the positive engagement ofthe lever end 28 in the recess 25. The adjusting fork 17 is displacedaxially along the guide axis 24 on the guide element 19 in the directionof the longitudinal axis 14. In this process, the axial slide 12performs an axial movement as a result of the first body contact and thesecond body contact with the adjusting fork 17.

According to the invention, the adjusting fork 17 is provided with theengagement recess 25 for the accommodation of the lever end 28, theengagement recess 25 and the first contact surface 35 and also thesecond contact surface 26 having conformal directions with respect tothe guide axis 24. The engagement recess 25 is arranged in the guidesection 18 of the adjusting fork 17.

FIGS. 3 and 4 are longitudinal sections of the exhaust gas duct sectionaccording to FIG. 1, wherein the momentums MV, MA acting on the diffuser10, which are generated at the adjusting fork 17 and the axial slide 12,are indicated. FIG. 3 shows the momentums which occur as the axial slide12 is moved in the direction of a first position, the so-called openposition. In this position, the orifice cross-section 8 is completelyopen. FIG. 4 shows the momentums which occur as the axial slide 12 ismoved in the direction of a second position, the so-called closedposition. In this position, the axial slide 12 is partially orcompletely inserted into the orifice cross-section 8. In the embodimentaccording to the invention, the momentum MV applied by the adjustinglever 20 to the adjusting fork 17 is completely or partially compensatedby the momentum MA generated at the axial slide 12.

FIG. 5 shows a diffuser from prior art. FIGS. 6 and 7 show the momentumswhich occur in a movement process. This indicates that a tiltingtendency due to an addition of the momentums cannot only not beeliminated but added up increasing the filtering forces.

The second recess 34 is advantageously designed to complement the firstend section 32 and the second end section 33 of the fork 17, wherein,for the location of the axial slide 12 in the adjusting fork 17, solidbody contact due to cohesive friction between the second recess 34 andthe first and second fork end sections 32 and 33 has to be provided.

In a further embodiment, the first fork arm 21 and the second fork arm22 have a groove-shaped recess facing the axial slide 12 each, in whicha ring which is annular or partially annular, which is permanentlyjoined to the axial slide 12 and which complements the cross-section ofthe groove-shaped recess can be accommodated.

In a further alternative embodiment, the adjusting fork 17 is designedas a single piece with the axial slide 12, the adjusting fork 17 and theaxial slide 12 each having a permanent connection at the first bodycontact and the second body contact.

1. A diffuser for a turbocharger having an adjustable turbine geometry,the diffuser (10) comprising an axial slide (12) and an adjusting device(16) for positioning the axial slide (12), the adjusting device (16)comprising an adjusting fork (17) having an opening (23) with a guideaxis (24) accommodating a guide element (19) and further comprising anadjusting lever (20) with a lever end (28), the adjusting fork (17)having at least one contact surface (35, 36), in body contact with theaxial slide (12), the adjusting fork (17) having an engagement recess(25) for the accommodation of the lever end (28), the engagement recess(25) with its contact surfaces (35, 36) being positioned between theguide axis (24) and a longitudinal axis (14) of the axial slide (12). 2.The diffuser according to claim 1, wherein the engagement recess (25) isprovided at side of a guide section (18) of the adjusting fork (17)facing the axial slide (12).
 3. The diffuser according to claim 2,wherein the guide section (18) is firmly joined to the adjusting fork(17).
 4. The diffuser according to claim 1, wherein the lever end (28)is movably accommodated in the engagement recess (25).
 5. A turbochargerfor an internal combustion engine, comprising a housing (2) with anexhaust gas duct section (3) through which exhaust gas can flow to aturbine wheel space in the housing (2) and wherein a diffuser (10) forchanging the admission of exhaust gas to the turbine wheel space isprovided in the exhaust gas duct section (3), the diffuser (10)supporting an axial slide (12), and an adjusting device (16) forpositioning the axial slide (12), the adjusting device (16) comprisingan adjusting fork (17) having an opening (23) with a guide axis (24) forthe accommodation of a guide element (19), the adjusting device (16)further comprising an adjusting lever (20) with a lever end (28), theadjusting fork (17) having at least one contact surface (35, 36), inbody contact with the axial slide (12), the adjusting fork (17) furtherhaving an engagement recess (25) for the accommodation of the lever end(28), the engagement recess (25) with the lever end (28) beingpositioned between the guide axis (24) and a longitudinal axis (14) ofthe axial slide (12)
 7. The turbocharger according to claim 5, whereinthe guide element (19) is supported in a contoured sleeve (13) on theside remote from the second spiral passage (5) and in the exhaust gasguide section (3) on the side facing the second spiral passage (5). 8.The turbocharger according to claim 5, wherein the guide element (19)and the opening (23) are cylindrical.
 9. The turbocharger according toclaim 5, wherein the adjusting fork (17) and the axial slide (12) have afirst body contact and a second body contact, the first body contact andthe second body contact being arranged symmetrically with respect to theguide axis (24) of the guide element (19).